In a medium mixing bowl, whisk marshmallow fluff and 1 cup whipped topping with a hand mixer until blended. Add pudding mix and blend until fully combined. Stir in 1 cup chopped cookies.
To build your cake, lay 4 ice cream sandwiches, side-by-side, on a freezer-safe serving platter; cover with half the pudding mixture. Repeat layers and top with remaining sandwiches. Frost with remaining whipped topping and garnish with remaining chopped cookies, mini marshmallows and chocolate sauce.